Avaya Business Communications Manager 5.0 - Planning and Engineering User Manual download pdf (Page 177)

VoIP overview 177

Nortel Business Communications Manager 5.0

Planning and Engineering

NN40170-200 01.03 Standard

August 2009

PVQM monitors a set of metrics which include

• packet loss

• inter arrival jitter

• round trip delay

• Listening R

These metrics and supplementary information provide you with valuable

insight into the real time quality of the call from the end-user perspective. This

information gives an indication of the type of problem, and can be used to

locate the source of the issue, thus accelerating the isolation and diagnostics

phase of problem resolution.

In addition to packet loss, inter arrival jitter and round trip delay, PVQM

monitors the “listening R” value. The R-Factor, as defined by ITU G.107 and

IETF 3611, is a call quality index that assesses network impairments such as

packet drops, jitter and round trip delay with consideration for the burstiness

and recency of these impairments. The Listening R metric provides you with

definitive answers about the actual QoS delivered to the telephone user. With

this metric, you see the raw data (such as jitter or packet drop rate), and a

summary of the effect of the data on the quality experienced by the user.

For example, a Warning Threshold for the listening R-value might be set at 80.

When voice quality drops below this value as measured at the telephone set

itself, an event is generated. The event notification is augmented with other

valuable state information, such as network loss rate, average rate of discards

due to jitter, average length of bursts, and presented as an alarm. Analysis of

the alarms and supplementary information in the alarm description helps you

identify and troubleshoot voice quality issues and proactively initiate

responsive actions.

Refer to Nortel Business Communications Manager 5.0 Administration and

Security (NN40170-603) for information on how to configure and use PVQM

functionality.

IP telephones in VoIP network

IP telephones offer the functionality of regular telephones but do not require a

hardwire connection to the BCM. Instead, they must be plugged into an IP

network, which is connected to the LAN or WAN on the BCM. Calls made from

IP telephones through the BCM can pass over VoIP trunks or across a Public

Switched Telephone Network (PSTN).

Nortel has several types of IP telephones that connect to the BCM through

Ethernet. The IP softphone 2050, which runs as a client application on a PC

or PDA, also connects to the BCM through the Ethernet.

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